Cannonball Express was usually Japanese-made from from Tange butted cromo steel. It's a very nice bike.
Don't try to convert to drops, it isn't worth the effort and you have some really nice old-school XT components.
Check for wear, esp in the transmission.
First try the bike for its riding position. The front looks a bit high. You can switch the bars to butterfly/trekking style, get some alt handholds and reuse your current bar controls.
Switch to some slick tyres, about 1.25-1.5" seems to be the choice for longer, endurance rides.